Predictably, very thin on actual logic. He waffles on about why marriage and stable couples are good for society, without giving any reason why this is exclusive to mixed-sex marriages. Eventually, after labouring the point, he rears his sock-puppet bogie man:

If same-sex marriage is legalised, schools will be forced to teach children the new definition of marriage – which will run counter to the wishes of many parents.

We know what will happen, for we have already had a taste of it – it will encourage religious discrimination. A marriage registrar from Islington believed in traditional marriage, and was disciplined by her employers for it. The elderly owners of a B&B believed in traditional marriage, and were successfully sued for it. Numerous Roman Catholic adoption agencies believed in traditional marriage, and were closed down for it.

These examples will be the thin end of the wedge if same-sex marriage is legalised.

There's no evidence the B&B owners turned away unmarried straight couples. Gay customers would have been refused even if they were married. Whether they believed in not-as-traditional-as-all-that marriage or not, it wasn't the basis of their discriminatory action.

If same-sex marriage is legalised, schools will be forced to teach children the new definition of marriage – which will run counter to the wishes of many parents.

Schools don't teach marriage. The archie's definition displeases plenty of parents itself. Here's a revolutionary idea: why don't we stop defining it at all? Let marriage mean what the spouses want it to mean. Discard tired old bollocks about it being the bedrock of anything. Judge not same-sex couples, unmarried couples, polyamory, singles — and thou shalt not be judged for writing reactionary crap in the Daily Mail.

For example, hospice, hospital and hotel all share a root but come into English from different languages. So there is a full aspirant on hospital and hospice, but only a semi* on hotel (which would have no aspirant at all in French).

So a hospital, and an hotel. In speech. Different rules in written English where pronunciation doesn't much matter.

*fill in your own jokes, I've got a headache.

The pain broke me, brotherhood relieved me, and from my wounds sprang a river of freedom.(Paul Dorey)Inscription on the Mémorial de la Paix, Caen.
How soon we forget.

I note that Carey was Archbishop of Canterbury from 1991-2002. He's no-nonsense and rightwing, the sort of leader we're always told the C of E needs instead of this wishy-washy tendency that thinks the enemy's war dead matter too.

So must have been a real golden age of full pews. Not my memory of that era, to say the least.

To risk cross-threading, I think Dawkins has been dead on with regard to the church trying to claim people as Christian who don't go to church or know anything about the Bible. You often hear that there are people who say they want something spiritual. So the church claims to speak for them.